Sweeten black tea with sugar. Add yeast and friendly bacterial cultures. Allow to ferment for several days. What do you get?

It's called Kombucha tea - a fermented beverage and "symbiotic colony of bacteria and yeast" - most commonly consumed for health benefits.

What health benefits?

A recent article in the Journal of Science of Food and Agriculture notes that Kombucha tea contains "potential hepatoprotective agents." Translation: some of the substances in Kombucha could possibly be good for the liver. (Remember that the liver is our body's main detox unit.)

Another report on Kombucha appeared in Food Research International. In laboratory tests, biochemists observed that this fermented beverage interfered with enzymes that digest starch. Is this good? Undigested starch in the human body might be a way of controlling blood glucose in people with diabetes, scientists theorize.

Other researchers in Switzerland found that Kombucha tea had "antimicrobial activity" - the ability to fight infections. They suggest that some of the fermented bacterial cultures in this tea might help fight off bad bacteria such as Candida (the microbe that causes yeast infections).

And herein lies the problem. While there seem to be a lot of studies that suggest potential benefits to consuming Kombucha tea, no studies to date have actually tested these hypotheses on humans.

Rats, yes. One recent study on rats with diabetes (really) reported in the Journal of Food and Chemical Toxicology that both unfermented black tea and fermented Kombucha tea possess healthful antioxidant properties. However, the properties of the Kombucha (fermented) tea were more effective than the black (unfermented) tea.

Most of us are not rats with diabetes, however. And unfortunately, along with these potential benefits are real safety concerns, say health experts.

The US Food and Drug Administration which evaluates reports of harm from food or drugs has received some pertaining to Kombucha, including a rare but fatal condition called "lactic acidosis."

"Use caution when making and drinking this tea," warns the FDA.

Other cautions come from the American Cancer Society (ACS): "Because several types of yeast and bacteria can grow under Kombucha tea's brewing conditions, different teas may contain different varieties (of cultures). Since cultures and preparation methods vary, Kombucha tea may contain contaminants such as molds and fungi, some of which can cause illness."

Lastly, cautions the ACS, "since the potential health risks of Kombucha tea are unknown, anyone with an immune deficiency or any other medical condition should consult a physician before drinking the tea. Women who are pregnant or breast-feeding should not use this tea.

Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences."

Potential benefits and potential risks. Stay tuned …

(Barbara Quinn is a registered dietitian and certified diabetes educator at the Community Hospital of the Monterey Peninsula. She is the author of the "Diabetes DTOUR Diet" (Rodale 2009) and the "Diabetes DTOUR Diet Cookbook" (Rodale 2010). Email her at bquinn@chomp.org.)